
412 Principles of Sustainable Energy Systems
© 2008 Taylor & Francis Group, LLC
at evaporator temperatures of 5°C or higher. Using a mixture of LiBr with some other
salt as the absorbent can overcome the crystallization problem. The NH
3
–H
2
O system
has the advantage that it can be operated down to very low temperatures. However, for
temperatures much below 0°C, water vapor must be removed from ammonia as much as
possible to prevent ice crystals from forming. This requires a rectifying column after the
boiler. Also ammonia is a safety Code Group B2 uid (ASHRAE Standard 34-1992), which
restricts its use indoors [18].
If the pump work is neglected, ...